Apparatus for sinking tubular work pieces



June 18, 1935. B. BANNISTER APPARATUS FOR SINKING TUBULAR WORK PIECES Filed March 14, 1933 3 Sheets$hee't l Z75 afar/h ya JL me 18, 1935. B, BANMSTER 2,005,125

APPARATUS FOR SINKING TUBULAR WORK PIECES Filed March 14, 1935 3 Sheets-Sheet 5 I ii t% i Patented June 18,1935

UNITED ,ISKTATES APPARATUS FOR SINKlNG TUBULAR/WORK rmo Bryant Bannister, Mount Lebanon, Pa. I Application March 14 1933, Serial N0. 660,718

1 Claim.

This invention relates to the manufacture of seamless pipes and tubes from east or rolled rounds, and particularly to that procedure in such operations where a tubular blank is materially 5 reduced in diameter and elongated, which is known in the artas sinking in contrast to light reductions known as sizing.

In the manufacture of small diameter merchant pipe" by the seamless process and in the 10 preparation of tubular blanks for cold drawing, particularly that process known as cross-rolling, it is desirable to first produce a seamless tubular blank having a diameter larger than'that of the finished pipe, and to reduce this diameter and control the wall thickness by a subsequent operation, which can be carried on at a reasonably high speed and low cost.

The usual sinking method employed-to make large reductions in the diameter of a tubular blank consists in passing the blank between a series of grooved power driven rolls arranged in pairs to form a circular pass, each pass having a smaller diameter than the preceding one. Reducing, or sinking,-mills of this type are costly to operate because of the high cost of maintenance and the difflculty in controlling wall thickness of the product. In addition, the loss occasioned by cropping unfit ends is high.

The method employed in my invention consists in feeding the tubular blank to be reduced between a pair of cone shaped power driven work rolls so arranged that their axes lie in parallel planes, but some distance apart. The axis of the tubular blank lies in a plane parallel to these two planes and substantiallymidway between them. The projections of the main roll axes upon the plane containing the axis of the tubular blank make equal angles with the axis of the blank. Each roll is driven by a suitable power source at 40 substantially the same rotative speed. These rolls also have the same ratio of expansion or taper as the tube while passing through the mill. This arrangement provides that the peripheral velocity of the work rolls bears a substantially uni- 45 form ratio to the peripheral velocity of the workpiece for all transverse sections through the converging portion of-the pass and rolls.

Positioned above and below the tube being diameter of the guide rolls provides a long are of Y 65 contact and consequently a moderate angle of reduction; that is to say, the conical section of the tube being reduced is of considerable length and the included or flow anglesbetween guide rolls is substantially the same as the angle included by the adjacent faces of the main rolls. 5 These guide disks are driven at approximately equal speeds and at a peripheral speed substantially greater than the speed of the main rolls, and consequently greatly in excess of the longitudinal travel of the pipe or tube. I

In a preferred embodiment of my invention a floatingmandrel slightly less in diameter than the inside diameter of the reduced tube is used. It is obvious that if the tube is reduced in dlameter the wall will increase in thickness, al- 15 though'the action of the guide rolls may tend to keep this thickening effect below that corresponding to the reduction in diameter. n The diameter is reduced and the wall thickened'until the metal of the tube is in contact with both the main rolls and the floating mandrel. From the gorge or narrowest portion of the pass to the outlet, the metal is reduced in wall thickness simultaneously with the reduction in diameter. In this portion of the pass the metal would be forced into a decidedly oval cross-section if .not restrained by the guide rolls, but owing to the restraining effect of the guide rolls and the high peripheral speed of these rolls in the direction of tube travel this potential ovality is turned into length. The tube, after reduction, may thus have the same wall thickness as the large diameter tube entering the mill, and will have a length greater than that of the entering tube in proportion to the cross-sectional area, of the entering tube as com- 85 pared to that of the tube as it leaves the mill.

. In a modified form of my invention a tapered v plug is introduced between the rolls andheld in position by a supporting bar which is free to rotate with the tube but restrained from moving forward with the tube. In this case it is preferable to provide a plug having the same taper as that defined-by the main rolls, so' that the wall thickness of the tube being reduced remains substantially constant, although if desired a slight reduction in wall thickness can be made as the diameter is reduced. v

If the guide roll speed is maintained sufficiently high there will be little tendency for the metal to bulge between various'roll contacts, but it may be desirable to introduce stationary guiding surfaces for a short distance at the large end of the reducing section-simply to restrain such bulging One object of my invention is to provide means whereby a tube is substantially reduced in di- 2 ameter and elongated without any substantial change in wall thickness.

A further object is the provision of a novel apparatus whereby the work-piece is elongated largely because of a reduction in diameter.

A still further object is the provision of a novel apparatus for reducing or sinking the tube diameter wherein the cross-sectional area of the.

tube is allowed to remain substantially uniform for the first portion of the pass and is then re-.

duced to effect elongation.

A still further object is the provision of novel means and apparatus for reducingor sinking the diameter of a tube by helical ro1ling"with out sub-' jecting the tube being reduced to twisting due to improper surface speed relations between the of my invention.

Figure 2 is a plan view thereof. Figure 3 is a transverse section taken along the lines ]1IIlI of Figure 2.

Figure 4 is a transverse section taken along the lines IV-IV of Figure 2.

Figure 5 is a transverse section taken on the line V-V of Figure 2.

Figure 6 is a composite view disclosing the re;

lationship of one work roll to one of the'guid rolls which is shown, together with a portion of the billet, in a plane substantially 90 from its true position in the mill.

Figure '7 is a view similar to Figure 3, in which I have disclosed a modified form of my invention.

Referring more particularly to the drawings, in Figure l the numeral 2: indicates a pair of work rolls disposed on opposite sides of the work-piece 4 and contacting with it, one above the horizontal center line of the work-piece and one below. The guide rolls 3 are disposed between the work rolls and contact the work-piece a greater distmice from its axis than tothe work rolls. This arrangement allows a slight ovality which is par-, ticularly necessary near the gorge" or most com stricted portion of the pass, to prevent the workpiece from binding on the mandrel. The guide rolls are driven by suitable means and have a peripheral velocity towards the outlet of the pass greatly in excess of the longitudinal travel or the piece out of the pass. A mandrel 5 is positioned within the hollow work-piece.

Referring to Figure 2, which is a plan of the apparatus illustrated in Figure 1, the pass formed by the work rolls 2 and guide rolls 3 has a converging portion 2* to the gorge" point of the pass. From: the "gorge" point and extending slightly in the direction of. the outlet end there is provided a substantially fiat or parallel work surface 2'', and from this point through the outlet end of the pass there is provided a diverging portion 2. 1

' The diameter or the work-piece in a vertical plane is limited by the guide rolls 3 so that in work rolls bears a substantially uniform ratio to the surface speed of the work-piece at any transverse section 015 work-piece and work roll. It slip or relative movement between roll and workpiece is neglected the surface speeds would be diameter.

in diameter just equals the vertical shrinkageand .1

identical at any section. This relationship of speeds avoids the tendency of the rolls to impart to the work-piece a greater angular velocity at one section than another, or the tendency to twist the work-piece is avoided.

In Figure 6 one work roll 2 is shown contacting with the work-piece 4, shown in section, and the mid-section of one guide roll 3 also contacting with the work-piece 4. This view of the guide roll and work-piece is shown rotated about the axis of the work-piece 90 degrees from its true position. As shown, the work-piece first contacts with the work rolls on line A-A and is rotated and advanced helically into the pass. As the horizontal distance between the work rolls decreases the work-piece assumes an oval section and contacts the guide rolls at point a. As the work-piece proceeds further into the pass the horizontal width continues to decrease but the guide rolls, due to their high velocity in the direction of the work-piece travel andeontact with it,- limit the vertical diameter ofthe oval by spinnin the metal into reduced diameter.

A portion of the metal of the work-piece is displaced in a longitudinal direction but the greater part of the displacement goes to increase wall thickness. Thus the work-piece is reduced in diameter with little change in cross-sectional area. When section B-B is reached the workpiece contacts the mandrel l and in traversing a helical path to section C-C of the pass the wall thickness is reduced to that desired in the reduced tube. As the metal is displaced between the work rolls 2 and the mandrel 5 there is a natural tendency for it to flow radially to increase the diameter of the work-piece. The tendency to flow radially produces great pressure against the guide rolls and because of their high velocity towards the outlet of the pass, the metal is diverted from radial to longitudinal flowand the workthe guide rolls 3 is, of course, assisted by stationary guides 3, which only contact the workpiece in the converging portion 2" of the work roll pass.

to section D'D are parallel to the mandreland reel out inequalities that remain in the wallof the work-piece. From section D--D to section E-E the faces of the work rolls diverge, allowing the horizontal diameter of the work-piece to increase with a corresponding decrease in vertical At section E-E the horizontal growth the work-piece assumes a circular section.

Figure 7 shows a modified form of my invention where a plug 6 is substituted for mandrel 3. ring 6 is supported on a bar I which is free to rotate but is restrained from longitudinal movement.

The contour and position of plug 6 is such that a.

ness of the work-piece is maintained or reduced and there is a gradual reduction in cross-sectional area of the work-piece instead of a more concentrated reduction as described for Figure 6.

The term sinking as used throughout the specification and claim is intended to define an operation whereinthe tube diameter is materially piece is lengthened. This restraining eflfect oI The faces of the work rolls from section C-C reduced, as contrasted with slight reductions in diameter commonly called sizing".

While I have shown and described. several specific embodiments oi'my invention, it will be understood that I do not wish to be limited thereto, since various modifications may be made without departing Irom the scope 0! my invention, as defined in the following claim.

I claim:

Apparatus for sinking tubular work pieces comprising two metal working rolls and a mandrel defining a pass, said rolls and mandrel being conhaving a convergent portion co-extensive with structed and arred to provide a reducing pass the major part of the length of said'rolls, a substantially short reeling portion, and a divergent portion, in combination with a powereactuated guide roll for guiding and assisting the work piece through the outlet end of the pass, said guide roll having its contact surface nearest the axis of the workpiece positioned adjacentsaid reeling 

